Nicer debug printing when op doesn't have an associated source line
Avoid incorrect heap addressing when retrieving a symbol's address
Bug fix: was not properly initializing the default values of output
params if they were written but never read. Most of the time, the output
param was written over in the shader body anyway, so this was not
noticed.  But in cases where it might not be assigned in the main shader
body, the default value was not present.
Reorder include directories for building LLVM bitcode so that the openimageio,
ilmbase and boost directories are ahead of any system directories given by
llvm-config --cxxflags.

This avoids the LLVM bitcode getting compiled against different library versions
than the rest of the code if multiple versions are installed.